Stop motion device for fabric producing machines



Nov.- 11, 1958 A. EDELMAN ETAL 2,859,603

STOP MOTION DEVICE FOR FABRIC PRODUCING MACHINES Filed June 12, 1956Sheets-Sheet 1 FIG RIHHHXHHHHHH INVENTORS ABRAHAM EDELMAN TuaoooaaLAsAR,

BY [A Ma,

ATTORN Y! Nov. 11, 1958 A. ED'ELMAN EIAL STOP MOTION DEVICE FOR FABRICPRODUCING MACHINES Filed June 12, 1956 4 Sheets-Sheet 2 liiiiii' ilINVENTORS N m 5 A L W mm O M B mml n T w ATTORNEYS' Nov. 11, 1958 'A.EDELMAN ETAL 2,859,603

STOP MOTION DEVICE FOR FABRIC PRODUCING MACHINES Filed June 12, 1956 4Sheets-Sheet 3 RECTIFIED I INVENTORS F l G 9 ABRAHAM EDELMAN fiTuaooouF.LASAR ATTORNEYS Nov. 11, 1958 A. EDELMAN ETAL 3 STOP MOTION DEVICE FORFABRIC PRODUCING MACHINES 4 Sheets-Sheet 4 Filed June 12, 1956 POWERSUPPLY CABINET DC 5 AC SIoNAL SuPPLIEs AuALgzI-za A c. VOLTAGE AMPLIFIERSTAB'L'ZER POWER AMPLIFIER l e- STOP RELAY 6 I Z SENSITIVITY LAMP A.c. IMITCH I AoJus'ruENT S|GNAL O LA TIME DELAY RELAY U KNITTER MOTOR C OUTMOTOR CONTROL stirs" SUSPENDED SHIPPER MANUAL CONTROL CABLE B R I OFKNITTER Moron W A RAIL I ifl 1 A/ REVERSING SCANNER Q R v'e, I ScANNERSWITCH QARRIAeE 3. I; Mo-ron LAMPQQZOLAMP SCANNER FAaRIc I MOTOR I GINVENTORS ABRAHAM EDELMAN Q. THEODORE LASAP ATTORNEYS Unite .S'I1QPMOTIONJJEVICEEUR FABRIC PRODUCING MACHENES Abraham Edelman, New York, N.Y., and Theodore :Lasar,;Fort:Lee, N. J., assignorstozPhotobell Company,New Y ork, N. Y., a partnership composedof Abraham v EdelmanandJohannaEdelman Application June 12, 1956, Serial No. 590,990 '151Glaims.(Cl.66-.166)

dividual threads. If any of the many possible needle faultsoccurs vorany of the threads breaks, the knitted fabric completed thereafter showsa continuing deffect.

In recent years automatic stop motion installations have been developed.These installations employ a scanning device whichrides back and forthacross the width of the fabric asit emerges from the knitting machineand continuously examines the knitted fabric close to the needle bar.The scanning device comprises a sourceof light illuminating successiveareas of the fabric tobe inspected and a pair of light sensitive devicessuch as phototubes which receive light from different portions of theilluminated area and control a stop circuit for the knitting machine.When the portions of the fabric scannedby the light receivers are bothflawless, the signals generated ,by the tworeceivers are in balance, butwhen there i a fault in the fabric suchfault manifests itself in a lightdifferential whichenergizes the stop circuit. As a result, the machineis stopped until it is manually restarted after the faultis remedied.Automatic stop'motions of this type permit the supervision of a greaternumber of machines by a single operator than was possible before thedevelopment of automatic stop motions thereby materially reducingdefective yardage and the costs of supervision. However, automatic stopmotions as heretofore known, have certain shortcomings and it is thegeneral object of the present invention to remedy these shortcomings.

As will be more fully explained hereinafter, the fabric while beingknitted vibrates and flutters somewhat at the areaof inspection. Suchmotions of the fabric, which are unavoidable in practice, produce smallvariations in the light reflected from the fabric as seen by the lightreceivers, and experience shows that the variations in the reflectedlight as caused by the motions of the fabric are sometimes sufiicient tostop the machine even though there is no defect in the fabric.

Accordingly, one of the objects of the present invention is to providenovel and improved scanning means, the light receivers of which see thevariations in the .reflected light as caused by vibrations andfluttering of the fabric below the level of the variations as caused byafault in the fabric and requiring a stoppage of the machine. As aresult, changes in the reflected light due to spurious signals resultingfrom the operational vibration and fluttering of the fabric cannotetfect an unnecessary and undesirable stoppage of the machine.

Another object of the invention is to provide novel and improved meansfor controlling the illumination of the fabric at the area of inspectionso as to keep this illumination substantially constant and independentof vari- Sttes Patent ations in the surrounding illumination. As isapparent,

variations. in thesurrounding illumination causing changes in therelative illumination of the fabric portions as seen and compared by thelight receivers, which reach the level of thechanges causedby a defectin the'fabric will also result in a stoppage of the machine.Consequently,

a constant illumination of theinspected areaseliminates this source ofunwanted stoppage.

Still another object of the invention is to provide novel and improvedmounting means which assure that the distance between the scanning meansand the fabric is maintained sufficiently-constant and uniform when 'andwhile the scanning means travels across the width of the fabric, even ifthe knitting machine has a very wide needle 'bar.

improved controlsassembly for controlling the reversal of the travel ofthe scanning mean at each edge ofthe fabric. The control assembly of theinvention affords the advantageof greater compactness than. theretoforeavailable thereby correspondingly-reducing the total width of theinstallation necessary to span the fabric.

Further objec s, features and advantages .ofthe invention will-bepointed out hereinafter and setforth in-the appended claims forming partof the application.

In the accompanying drawing several preferred embodiments oftheinventionare shown byway ,of illustration and notby way of limitation.

.;In the drawing:

Fig. lis adiagrammatic view ,of aknitting machine and the fabricemerging-therefrom.

Fig.2 is a plan view ofa stop motioninstallationaccordingtotheinvention.

Fig. 3 is an elevationalside view of Fig. 2.

Fig. 4is a diagrammatic view of the optical systemof the scanningrmeans.

Fig. 5 is atypical circuitsystem for producingauniform illumination oftheareato be inspected.

Figs. 6 and 7 are graphsexemplifying the effectof the circuit systemaccording to Fig. 5.

Fig. 8 is a plan view of a modification-of the control means forreversing the travel of the scanning means...

Fig. 9 is an elevational side view of Fig. 8.

Fig. 10 is a further elevational front view of the. scanninginstallation.

vFig. 11 is an elevational side view of Fig. 10, and

Fig. 12 is a block diagram of the entire installation.

Referring first to the. diagrammatic Fig. 1, this figure shows warpthreadsl guided to a needle bar 2. While only rather fewsthreads areshown it should be-visualized that in actual practice there may. bethousands 01f? Warp threads. Thefabric 3 which emerges from the needlebar is guided to a take-up roller 4 upon .which it is rolled up. Theline of inspection across which the scanning means travels back andforth is indicated by .a dashed line 5 The figure further showsas-curved lines 6 a typical pattern of fabric waves. These fabric wavesare unavoidable-in practice. The distance from peak. to peak of adjacentwaves varies. The distance may be as short as two to four inches and itmaybe considerably longer, but the wavesare always present. As aresultof the two light receivers of the scanning means previouslyreferred to, one may viewfabric at the top of a wave-while .the other;is viewing fabric at the bottom of a wave. ,As-is evident,light-refleotedifrom fabric at the bottom .of a wave hasan intensitydiflerent from that reflectedfrom the peak of a wave. Since the lightvreceivers and with the entire stop motion installation are controlled bya balance or unbalance of reflected light, the aforementioned differencein the reflection caused by the different location of the fabricportions viewed by the light receivers may be and often is sufficient toproduce a false indication that there is a defect present in the fabricwith the attendant unnecessary stoppage of the machine. 'A stoppage of amachine constitutes not only a loss of time, but also results inundesirable stop marks on some fabrics.

As mentioned before, the distances from peak to peak of adjacent Wavesmay and do vary, but no instance has been observed in which the distancefrom peak to peak is less than about two inches. The present inventionis based upon this observation and the scanning means of the inventionpermits to view portions of the fabric which are spaced extremely closeto each other. In actual practice the viewed portions of the fabric maybe spaced apart about 4 inch or less. This affords the advantage thatthe effect of the waves upon the reflection of light as seen by thelight receivers is nullified since both the receivers see approximatelythe same condition on the fabric.

All the features of the invention which have been previously describedor will be described hereinafter serve the purpose of attaining uniformand constant conditions to avoid signals due to causes other than actualdefects in the fabric.

Turning now to the figures showing the installation according to theinvention, the exemplified installation comprises a scanning devicegenerally designated by 10. This device rides back and forth across thewidth of the fabric on a traverse rail generally designated by 11. Therail is mounted at each end on a mounting device generally designated by12. A control means generally designated by 13 serves to control thereversal of the scanning device at the end of each travel in eitherdirection.

Fig. 4 shows the optical system of the scanning device. The opticalsystem comprises two lamps 15 and 16 the specific features of which willbe more fully explained in connection with Figs. through 7, two lightreceivers 17 and 18 such as photo tubes or crystals, a lens system 19and a beam splitter 20. The beam splitter is shown as a thinly silveredmirror. Such a mirror has the optical property that it passes part ofthe incident light and refleets the remaining part of the light. As canbe seen in the figure, light receiver 17 is mounted in alignment withthe optical axis of the lens system whereas light receiver 18 is mountedat a right angle thereto. The lens system which views the area of thefabric to be inspected and brightly illuminated by lamps 15 and 16, isfocused upon the light sensitive part of receivers 17 and 18. The beamsplitter may be mounted in any suitable manner. By way of example, a.casing 21 is shown the respective walls of which have each an opening22 the area of which is such that they will pass light from an arealarger than the fabric portion to be inspected by each light receiver.Light beams actually received by the light receivers are controlled bymasks 23 and 24 interposed between the beam splitter and each lightreceiver. While the masks are shown as a wall of a casing 25 and 26respectively, it is apparent that the masks may also be in form ofseparate discs or plates. Each mask has a small opening 27 and 28respectively. A circular aperture in the mask has been found to be mostsuitable. The essential feature of apertures 27 and 28 is that the twoapertures are correlated with each other, the beam splitter and the lenssystem so that the two receivers will sequentially receive light fromdifferent but closely adjacent portions of the fabric area inspected ateach moment. As is evident, the relative location of the viewed fabricportions can be very accurately controlled by slightly varying therelative location of the apertures. The difference in the location ofthe inspected fabric portions is indicated in the figure by dashed linesindicating different beams received by receivers 17 and 18. To shieldthe phototubes from the ambient fluctuating illumination each lamp isset in a shield 30 and 31 respectively which shields also act asreflectors. In addition the forward part of the bulb of each lamp may befrosted thereby avoiding shadows due to bulb imperfections.

While the aforedescribed reflector shields and the frosting of the lampbulbs, if used, prevent a disturbing effect due to the ambientillumination upon the fabric as seen by the light receivers 17 and 18,care must further be taken that the yield of light of lamps 15 and 16 issuch that it does not cause spurious signals.

The source of current which is used for the lamps is for all practicalpurposes a 60 cycle A.-C. line. It has been found that if thealternating current is applied directly to the lamps, the 60 cyclefluctuations in the supply voltage cause cycle fluctuations in thefilament temperature and that the changes in the light output caused bysuch fluctuations are large enough to interfere with the defectdetecting operation. In a typical case, the light from the lamps wouldfluctuate 120 times per second reducmg the light output 2% at eachfluctuation. Defects may produce a light reduction of the same order ofmagnitude which would interfere with the discovery of many defects.

The circuit system according to Fig. 5 serves the purpose of eliminatingor at least reducing to a harmless level the 60 cycle fluctuations inthe supply voltage.

There is shown a step-down transformer 37 the primary terminals 38 ofwhich are fed with A.-C. line voltage and which converts the lightvoltage to a suitable low voltage. This voltage is full-wave rectifiedby a rectifier 32 and filtered by series inductance means 33 andshunting capacitors 34 and 35 before being fed to lamp filaments 15' and16' respectively. While only one inductance and two capacitors areshown, it should be understood that a greater number of inductances andcapacitors may be employed.

By rectifying the A.-C., using a full-wave rectifier as shown, the A.-C.is converted into D.-C. having a superimposed ripple of 120 cycles andits harmonics. Fig. 6 shows the rectified A.-C. and the correspondingoutput of light. As is apparent from the previous description and Fig.6, the light output produced as the result of the rectification is onlyslightly better than the original A.-C. The aforementioned filters serveto remove the ripple. While the capacitors and the inductances arecapable of removing the ripple to a satisfactory extent, a

rather large and expensive filter network is necessary to achieve thepurpose. According to a further improvement of the invention also shownin Fig. 5, the ripple is rendered harmless by adding highly eflicientyet very inexpensive circuit components.

it has been found that the thermal inertia of the filament of a lamp asnow available in the market is such that the filament responds to amaterial extent by changing its temperature and with it the output oflight at a rate of 120 cycles per second, but that it cannot respond ata rate of 240 cycles per second (which is the second harmonic of 120cycles), or at higher frequencies. Hence, the filtering means need to beefiicient only at 120 cycles but do not require efliciency at theharmonics of 120 cycles.

According to the invention a shunting capacitor 36 is provided and theinductance 33 is tuned to resonance at 120 cycles per second. As aresult, the impedance of the filter network to 120 cycles per second isextremely high. The resulting light output has almost no 120 cycleripple. While the lamp current shows higher frequencies, the lightoutput of the filament does not show the same. Fig. 7 shows the filteredD.-C. and the corresponding light output. As may be noted, the lightoutput is practically constant. Consequently, the lamps will supply auniform illumination to the fabric area to be inspected.

As has been in Figs. 2 and previously explained and can best be seen 3,the scanning device 10 travels back and forth on rail 11 across thewidth of the fabric. The rail must span the fabric and ,is frequentlyofconsiderable length so that it will sag unless made of uneconomicallyheavy material. Sagging of the rail obviously causes a change in thedistance between the opticomprising; two plates 41 and 42 joined by anysuit- :able means such .asa cross bar 43. The bracket mounts :a. devicefor exerting a, downward pressureupon the rail .portions overhanginggrippers 40. These means are shown as a screw 44 which can be secured inposition by a set screw 45. As is evident, each gripper ,40 formsineifectthe fulcrum of a two-arm lever sothat-by raising or loweringscrew 44 the long arm of the lever, or in .other words the long middleportion .of the rail can be lowered or raised to compensate for saggingof-the ,rail. Each bracket is supported on a screw bar 46 which isthreaded in a stanchion 47 and can be adjusted, as to height by anysuitable means such as a lock nut 48. The base of the stanchion on oneside of the scanning assembly mounts a motor assembly 49driving a pulley50 for supplying the power to move the scanning device back and forth,and a control box 51 housing the equipment required for controlling themotor and the reversal thereof. The motor assembly and the controlassembly .should be visualized asbeing of conventional design and adetailed description thereof is not essential for the understanding ofthe invention. For the sake, ofclarity .of illustration the motor andthe control assembly are shown rotated through an angle from the actualoperating position.

The aforedescribed components of the scanning devicearemounted on acarriage 52. To pull the carriage .along rail 11, one end of a drivecord or belt such as anylon-cord 53 is attached tothe carriage byanysuit- ;able means such as a-hooki54. The cord-is guided over a; roller55 disposed between bracket arms {Hand 42,

:motor driven pulley 50, asecondroller 561also.dispose d between arms 41and 42, a return roller-.(notshown) -on:the mounting means supported onthe other-stanchion and back to the carriage to which it is attachedbyany suitable means such as a hook 57. Tension springs 58 and 59 arepreferably included-inthe drive cordto-hold the cord taut and reducingjerks when the movement .of carriage 52 is reversed. As is apparent,rotation of pulley 50 will pull the carriage of the scanning devicealong the rail in one or the other direction depending upon therotational direction of the motor.

To reverse the direction of the carriage at eachend ofits travel, areversing cam 60 is provided. This cam is shown in form of a baroutwardly slanted at each end to facilitate coaction with a roller 61.This roller is supported on an arm 62 the position of which controls aswitch 63 in a manner well known in the art. Each switch is mounted on abracket64 secured by any suitable means such as screws to the raillaterally protruding therefrom as can best be seen in Fig. 2. Bracket.64 also mounts a springy bumper 65 which coactswith a suitable abutmentsurface on the carriage if the reversing action failsto operate.Actuation of'switch 63 by engagement of its roller 61 with respectiveslanted end of cam 60 controls the control equipment in box 51 so as toeifect reversal of the motor.

A corresponding arrangement of a switch 63 and a bumper 65 are providednear the other end of the rail also. The motor and the motor controlshown in Figs. 2 and 3 as being associated with the left hand stanchionmay of course alternativelybe associated with the other stanchion.

Figs. 8 and 9-show a modification of the reversal conrespondingly closerto the rail.

This entails correspondingly long protect the cables and trol'which'affords the advantage, of every; compact deg Th a s ly-tor these fig r i-id s gn d-ito occupy 'a minimum space between the --trave,rse rail 11and the take-up roll of the knitting machine.

According to the design of Fig. 2, roller 61 whichby coaction withreversing cam controls the r spective switch63 isdisposed on the farsideof the control assembly relativeto rail 11 and cam 60 is-correspondinglywidely spaced from the rail. The design of Figs. 8 and 9 shows alocation of roller 61 an d arm 62 which is closely adjacent to rail 11.The relocation of theswitch and the associatedcomponents permits to movecam :60 cor- As a result, the overall width of the control assembly asseen .in the direction of travel of the fabricrelative to the rail ismaterially reduced.

Figs. 10 and llshow anoverall elevational front view and side viewrespectively of-the entire assembly. For sake of clarity certaindetailsshown in Figs. 2' and} have been omitted. Figs. 10 and 11 alsoshow anarrangementfor guiding the electric connections betweenthe-scanning device 10 and ;a control cabinet which houses'theelectrical components'controlledby the signals received from thescanningdevice-and in turn controlling -the;stopping of the machineupondetection of adefect .in.the fabric.

As is apparent from the previous description, thescanning. device movesthrough a rather considerable distance.

.cableswhich are subject to damage by entanglement andundue flexing. To

also to provide; means :forconveniently mounting the-stanchionsof theassembly both stanchions 47 are extended beyond the mountings for therail. The extendedpartof the stanchions lends itself .conveniently tobracing the entire assembly to a wall, the .machine, etc. -by-means ofbrackets such as bracket-71.

The extension of oneiof the stanchions may'also be used tomount controlcabinet 70. The upper ends of both stanchions are joined by a bar 72which mounts a trolley rail 73. On this rail rides a carrier 74whichguides the cable 75 leading from the scanner to controlcabinet 70. As isevident, carrier 74 will move along the trolley ,railwhen the scannercarriage travels backand forth on traverse rail 11 thereby assuring thatcable 75 cannot become entangled with any parts of the assembly or beunduly flexed.

Finally, the block diagram of Fig. 12 shows the electric components ofthe entire assembly. The coaction of the several electrical componentsof the assembly is essentially self-evident from the legends applied-tothe block diagram. The circuit system which is controlled by the signalsreceived from the light receivers such as photo tubes 17 and 18 does notconstitute part of the present invention and need hence, not to bedescribed or shown in detail. It suffices to state that loss of lightfrom both photo tubes simultaneously tends to balanceout whereas loss oflight sequentialy tends to cause an :unbalance which stops the machine.Circuit systems suitable for the purpose are fully described in Patent2,7 1.1,- 094 issued June 21, 1955 in which one-applicant-herein is oneof the inventors.

The operation of the installation as hereinbefore described, is asfollows:

The traverse rail may be inserted between the stanchions with a slightupwardly arching camber to compensate for the weight of the scanningdevice and the rail. After the rail is installed it is adjusted by meansof set screw 44 so that the spacing between the fabric Y portance are inthe form of lines which travel-'with-the fabric movement, that is,approximately perpendicular to the movement of the scanner. As a result,a defect in form of a line will be viewed sequentially first by onelight receiver and then by the other. Due to the aforedescribeddistortions of the fabric as it emerges from the needle bar, the linedefect is capable of being at different angles to the direction of thescanner movement. For example, it may be at 30 to the direction of thescanner movement on one side and at 150 on the other side. Due to theprovision of circular or approximately circular apertures 27 and 28 thetwo light receivers may still view such defect sequentially.Furthermore, by adjusting the size of the apertures lack of uniformityin the .sensitivity of the light receivers and in the transparency ofbeam splitter 20 can be conveniently compensated. Light receivers forinstance photo tubes as commercially available do not have a sensitivitysuificiently identical for the purpose. Similarly, thinly silveredmirrors as used for the beam splitter reflect considerably more lightthan they will transmit and the reflected light does not have the samespectral composition as the transmitted light. As previously mentioned,all such variations may 'be conveniently and precisely corrected bysuitable selection of the size of the apertures 27 and 28. To facilitateadjustment of the apertures the same may be formed by shutters forinstance of the iris type, or by employing simple mechanical slideswhich vary the efiective aperture.

Whenever the carriage reaches one edge of the fabric the reversing cam60 actuates the respective miniature switch thereby reversing thedirection of travel of the carriage. Upon the detection of a defect theresulting unbalance of the light receivers generates signals activatingthe relay for stopping the machine and also energizing a signal light asindicated in Fig. 12.

While the invention has been described in detail with respect to certainnow preferred examples and embodiments of the invention it will beunderstood by those skilled in the art after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention, and it isintended, therefore, to cover all such changes and modifications in theappended claims.

What is claimed as new and desired to be secured by Letters Patent, is:

1. In a stop motion device of the kind wherein a scanning meanstravelling across the width of an illumin'ated fabric inspects thefabric as it emerges from a fabric handling machine and stops themachine upon detection of a defect in the fabric, a scanning meanscomprising lens means facing the fabric area under inspection, two lightreceiving means, light deviating means interposed between said lensmeans and each of said light receiving means, said light deviating meansdirecting a direct beam upon one light receiving means and a second beamupon the other light receiving means, said lens means being focused uponthe light receiving means, a mask disposed in front of each of saidlight receiving means, each of said masks passing light incident fromdifferent but immediately adjacent portions of the fabric area underinspection to the respective light receiving means, and control meanscontrolling a stop circuit for the machine and controlled by anunbalance in the light received by said two light receiving means fromsaid adjacent fabric portions.

2. In a stop motion device of the kind wherein a scanning meanstravelling across the width of an illuminated fabric inspects the fabricas it emerges from a fabric handling machine and stops the machine upondetection of a defect in the fabric, a scanning means comprising lensmeans facing the fabric area under inspection, two light receivingmeans, one disposed in the optical axis of said lens means and the otherat an angle thereto, beam splitting means interposed between said lensmeans and each of said light receiving means for directing a direct beamupon one light receiving means and a deflect ed beam upon the otherlight receiving means, said lens means being focused upon the lightreceiving means, a mask disposed in front of each light receiving means,each of said masks passing light incident from different but immediatelyadjacent portions of the fabric area under inspection to the respectivelight receiving means, and control means controlling a stop circuit forthe machine and controlled by a difference in the light received by saidtwo light receiving means from said adjacent fabric portions.

3. A stop motion device according to claim 2, wherein each of said maskshas a circular aperture therethrough, the positions of said aperturesrelative to the beam splitting means and the respective light receivingmeans being difierent one from the other to pass light from saidadjacent portions of the fabric area under inspection.

4. A stop motion device according to claim 3, wherein said apertures aredisposed in a spatial relationship such that the area portions underinspection are scanned sequentially in the direction of travel of thescanning device.

5. A stop-motion device according to claim 1, wherein said scanningmeans comprises a source of light including an incandescent lamp, and acircuit system for feeding the lamp filament with a voltage of acharacter to which the thermal inertia of the lamp filament issubstantially nonresponsive whereby the luminous output of the lamp isapproximately constant.

6. A stop motion device according to claim 5, wherein said circuitsystem comprises full-wave rectifying means converting an A.-C. supplyvoltage for the source of light into a D.-C. voltage having superimposedcycles, and filter network means filtering the rectified voltage,

said filter network means comprising capacitance means connected inshunt to said incandescent lamp and a resonance network connected inseries therewith, said resonance network including capacitance means andinductance means connected in parallel, said inductance means beingtuned to resonance for imparting to said filter network an impedancevalue at which the resulting filtered D.-C. voltage fed to the lampfilament is substantially free of cycles below the number of cycles towhich the thermal inertia of the lamp filament is responsive.

7. In a stop motion device of the kind wherein a scanning meanstravelling across the width of an illuminated fabric inspects the fabricas it emerges from a fabric handling machine and stops the machine inresponse to a defect in the fabric, a traversing assembly for traversingsaid scanning means across the width of the fabric to be inspected, saidassembly comprising a traverse rail spanning the width of the fabric,and mounting means at each end of said rail, each of said mounting meansincluding a rail support upon which the rail rests at a point inwardlyspaced from the respective end thereof, and a rail loading means at eachend of said rail, each of said loading means applying a downwardlydirected load to the rail portion protruding beyond the respectivesupport thereby exerting an upwardly directed force upon the middleportion of the rail between said two mounting means to compensate for asagging of said middle portion.

8. A stop motion device according to claim 7, wherein each of said railloading means is adjustable for applying a variable downward pressure tothe respective protruding rail portion.

9. A stop motion device according to claim 8, Wherein each of saidadjustable loading means comprises a pressure member mounted axiallydisplaceable on the respective mounting means and engageable with therespective protruding rail portion.

10. A stop motion device according to claim 9, wherein said pressuremember is a screw threaded through the respective mounting means.

.11. A stop motion device according to claim 7, wherein said mountingmeans comprise two stanchions each mounting one of said rail supports, atrolley rail joining the upper ends of said stanchions', and a carrierslidably suspended from said trolley rail for guiding electrical wireconnections for said scanning means.

12. In a stop motion device of the kind wherein a scanning meanstraveling across the width of an illuminated fabric inspects the fabricas it emerges from a fabric handling machine and stops the machine upondetection of a defect in the fabric, a scanning means comprising a lensmeans facing the fabric area under inspection, two light receivingmeans, light deviating means interposed between said lens means and eachof said light receiving means, said light deviating means directing onelight beam upon one light receiving means and a second beam upon theother light receiving means, said lens means being focused upon thelight receiving means, a mask disposed in front of each of the lightreceiving means, each of said masks passing light incident fromdifferent but immediately adjacent portions of the fabric area underinspection to the respective light receiving means, control meanscontrolling a stop circuit for the machine and controlled by anunbalance in the light received by said two light receiving means fromsaid adjacent fabric portions, a traversing assembly for traversing saidscanning means across the width of fabric to be inspected, said assemblycomprising a traverse rail spanning the Width of the fabric, andreversing control means comprising a controlled means mounted near eachend of said traverse rail and a controlling means on the scanning meansmoving in unison therewith, each of said controlled means includingreversing switch means having an actuating arm pivotal into a positioneffecting reversal of the movement of said scanning means and saidcontrolling means including an actuating cam secured to the scanningmeans and slidably engaging the respective switch arm at the end of eachtraverse for guiding said arm into its reversing position.

13. A stop motion device according to claim 12, wherein said switchactuating element comprises a pivotal arm, and said actuating camcomprises a bar having slanted end portions for slidable engagement witheither one of said arms to pivot the respective arm into its reversingposition.

14. A stop motion device for a fabric producing machine comprising, incombination, a frame structure ineluding two uprights and a cross railhorizontally extending between said two uprights, scanning meansslidably supported by said rail for scanning a fabric passing under therail as to defects in the fabric, drive means mounted on one of saiduprights and drivingly connected with said scanning means for drivingthe latter back and forth on said rail, rail adjustment means on atleast one of said uprights for adjusting the perpendicular distancebetween the scanning means and the fabric passing thereunder to auniform distance along the length of the rail, a second cross railextending between said two uprights above said first rail, a carriageslidable on said second rail, electric control means controlled by saidscanning means and controlling the operation of the machine for stoppingthe same upon detection of a defect by the scanning means, and aflexible electric cable connecting said scanning means to said controlmeans, said cable being attached to said carriage for guidance by thesame during the traversing motion of the scanning means on said firstrail.

15. In a stop motion device of the kind wherein a scanning meanstravelling across the width of an illuminated fabric inspects the fabricas it emerges from a fabric handling machine and stops the machine inresponse to a defect in the fabric, a traversing assembly for traversingsaid scanning means across the width of the fabric to be inspected, saidassembly comprising a traverse rail spanning the width of the fabric,mounting means at each end of said rail, each of said mounting meansincluding a rail support upon which the rail rests at a point inwardlyspaced from the respective end thereof, and adjustable rail loadingmeans exerting upon the middle portion of the rail between said mountingmeans an upwardly directed variable force to compensate for a sagging ofsaid middle portion of the rail by the weight of the scanning means.

References Cited in the file of this patent UNITED STATES PATENTS2,290,257 Stanley et a1. July 21, 1942 2,346,240 Thomas Apr. 11, 19442,413,486 Denyssen Dec. 31, 1946 2,611,097 Stanley et a1. Sept. 16, 19522,711,094 Edelman et al. June 21, 1955

